Anatomy - Pectoral girdle

Pectoralis Minor

with ribs fixed, draws scapula downward and forward; with scapula fixed, draws rib cage superiorly

Serratus Anterior

Rotates scapula so its inferior angle moves laterally and upward; Prime Mover to protract and hold scapula against chest wall; abducts and raises arm in horizontal movements BOXER MUSCLE; protracts shoulder

Trapezius

Stabilizes, raises, retracts, and rotates scapula; middle fibers retract (adduct) scapula; superior fibers elevate scapula (shrugging) or help extend head with scapula fixed; inferior fiber depresses scapule; prime Mover shoulder elevation (along with Levator Scapulae)

Levator Scapulae

Elevates and deducts scapula; works with superior fibers of trap to tilt glenoid cavity downward, scapula fixed flexes neck to same side

Rhomboids Major & Minor

Stabilized scapula; work together to retract (adduct) scapula “squaring shoulders”; rotate scapula downward (lowering arm against resistance)

Pectoralis Major

Prime mover of arm flexion; rotates arm medially; adduct arm against resistance; with scapula fixed, pulls rib cage upward thus helps climb, throw, push

Deltoid

Prime mover of arm abduction - all fibers contract together; anterior fibers flex & medially rotate humerus posterior fibers extend & laterally rotate arm

Latissimus Dorsi

Prime mover of arm extension; powerful arm adductor; medially rotates arm; brings the arm down in a power stroke, as in hammering, swimming, and rowing

Rotator cuff

Group of muscles that provide the shoulder with stability & help to control the joint during rotation. Act as synergists in angular & rotational movements of the arm. Sports that involve a lot of shoulder rotation put these muscles under stress (pitching, bowling, swimming)

Subscapularis - RC

Chief medial rotator of humerus; assisted by pec major; hold head of humerus in glenoid cavity

Supraspinatus - RC

Initiates abduction; helps prevent downward dislocation of humerus

Infraspinatus and Teres Minor - RC

Rotates humerus laterally; helps hold head of humerus in glenoid cavity

Teres Major

Extends, medially rotates, and adducts humerus; synergist of latissimus dorsi